Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $234.49   5.201%   $246.6858   $246.69   $246.70   $246.70  
  Purchase #2 $189.46   9.427%   $207.3204   $207.32   $207.30   $207.30  
  Purchase #3 $15.30   5.606%   $16.1577   $16.16   $16.15   $16.20  
  Purchase #4 $73.47   13.152%   $83.1328   $83.13   $83.15   $83.10  
  Purchase #5 $216.65   10.606%   $239.6279   $239.63   $239.65   $239.60  
  Purchase #6 $193.27   8.231%   $209.1781   $209.18   $209.20   $209.20  
  Purchase #7 $89.85   3.168%   $92.6964   $92.70   $92.70   $92.70  
  7 purchase totals = $1,012.49       $1,094.7991   $1,094.81   $1,094.85   $1,094.80